Steering transmission for electromechanical steering system for a vehicle and electromechanical steering system for a vehicle

Abstract

A steering transmission for an electro-mechanical steering system for a vehicle includes an electric motor, a servo transmission, and an angle transmission for connecting a steering column of the steering system to a control stalk of the steering system. The angle transmission is a mechanically driven recirculating-ball transmission with a ball nut, which is engaged with a segment shaft of the steering transmission that is/can be connected to the steering stalk. A spindle of the recirculating-ball transmission is continuous. The spindle is connected to an output shaft of the servo transmission on one side. The servo transmission is/can be driven by the electric motor.

What is claimed is: 
     
       1. A steering transmission for an electromechanical steering system for a vehicle, comprising:
 a housing; 
 an electric motor comprising a rotor shaft; 
 a servo transmission, wherein
 the servo transmission is an eccentric planetary transmission, 
 the eccentric planetary transmission has a common planet wheel, 
 the common planet wheel meshes with first and second ring gears, wherein a difference in the number of teeth between the first and second ring gears is greater than or equal to 1, wherein the first ring gear is fastened to the housing and is not able to rotate, and 
 the planet wheel is mounted eccentrically on a carrier which is directly connected to, and drivable by, the electric motor; and 
 
 an angle transmission for connecting a steering column of the steering system to a control stalk of the steering system, wherein 
 the angle transmission is a mechanically driven recirculating-ball transmission with a ball nut which is engaged with a segment shaft of the steering transmission that is connectable to the control stalk, 
 a spindle of the recirculating-ball transmission is continuous, 
 the spindle is directly connected to the second gear via a shaft-hub connection, wherein the second gear defines an output shaft of the servo transmission, and 
 the servo transmission is drivable by the electric motor. 
 
     
     
       2. The steering transmission as claimed in  claim 1 , wherein
 tips of teeth on the planet wheel are cut away to define different engagement cross sections. 
 
     
     
       3. The steering transmission as claimed in  claim 1 , wherein
 the planet wheel is mounted in an adjustable manner on a carrier in order to adjust a gearwheel clearance of a gearwheel engagement between the planet wheel and at least one of the two ring gears. 
 
     
     
       4. The steering transmission as claimed in  claim 1 , wherein
 tooth regions of the planet wheels and/or the ring gears are formed with a profile shift. 
 
     
     
       5. The steering transmission as claimed in  claim 1 , wherein
 tooth regions of the common planet wheel and/or the ring gears are formed with a profile shift. 
 
     
     
       6. The steering transmission as claimed in  claim 1 , wherein
 the ball nut of the recirculating-ball transmission has a linear guide which is configured to absorb radial loads introduced by a toothing between the segment shaft and the ball nut. 
 
     
     
       7. The steering transmission as claimed in  claim 6 , wherein
 the linear guide is a plain bearing. 
 
     
     
       8. The steering transmission as claimed in  claim 6 , wherein
 the linear guide is a multi-layer plain bearing or a plastics plain bearing. 
 
     
     
       9. The steering transmission as claimed in  claim 6 , wherein
 the linear guide is a rolling bearing. 
 
     
     
       10. The steering transmission as claimed in  claim 6 , wherein
 linear guide is a needle bearing or a combination of a needle bearing and a rolling bearing. 
 
     
     
       11. An electromechanical steering system for a vehicle, comprising the:
 a steering column; 
 a control stalk; and 
 a steering transmission connecting the steering column and the control stalk, the steering transmission comprising: 
 a housing; 
 an electric motor comprising a rotor shaft; 
 a servo transmission, wherein
 the servo transmission is an eccentric planetary transmission, 
 the eccentric planetary transmission has a common planet wheel, 
 the common planet wheel meshes with first and second ring gears, wherein a difference in the number of teeth between the first and second ring gears is greater than or equal to 1, wherein the first gear is fastened to the housing and is not able to rotate, and 
 the planet wheel is mounted eccentrically on a carrier which is drivable by the electric motor; and 
 
 an angle transmission for connecting a steering column of the steering system to a control stalk of the steering system, wherein 
 the angle transmission is a mechanically driven recirculating-ball transmission with a ball nut which is engaged with a segment shaft of the steering transmission that is connectable to the control stalk, 
 a spindle of the recirculating-ball transmission is continuous, 
 the spindle is directly connected to the second gear via a shaft-hub connection, wherein the second gear defines an output shaft of the servo transmission, and
 the servo transmission is drivable by the electric motor.